Instantiate a class once per parameter in JUnit - junit

Question

So I'm trying to run tests that will evaluate certain properties of different websites. The actual evaluation is being handled by a pay-per-call resource, so I want to minimize the number of times I generate the resource. Also, I need this to run in JUnit to fit into a larger automated test suite.
I've been doing this with parameterized tests so far, but I just learned that they instantiate a new instance for each test method.
Now I'm trying to figure out a way to have the resource created just once for each parameter that is being fed into the constructor of my testing class. #BeforeClass does it just once, and #Before does it once before each test.
All the help topics I've been able to find have dealt with creating expensive resources once for all tests, but in this case I need the resource to be recreated for each new set of parameters.
I've written some example code / output below to better show what I'm looking for:
#RunWith(Parameterized.class)
public class MyTestClass {
private static Resource expensiveToCreateResource;
public MyTestClass(String url) {
System.out.println("Constructing resource for " + url);
expensiveToCreateResource = new Resource(url); //This is getting created 4x, which is wrong
}
#Parameters
public static Collection<Object[]> data() {
return Arrays.asList(new Object[][] {{"url1"},{"url2"}});
}
#Test
public test1() {
expensiveToCreateResource.method1();
System.out.println("test1");
}
#Test
public test2() {
expensiveToCreateResource.method2();
System.out.println("test2");
}
}
would produce output:
Constructing resource for url1
test1
test2
Constructing resource for url2
test1
test2
Any ideas / solutions? Thanks.

Answer 1

If you want to have the class instantiated once per parameter, you'll have to write your own JUnit test runner. Instead I'd try to cache the information as needed, e.g. in a static map that maps URLs to resources.